1. Field of the Invention
This invention relates to a mold and a method for molding a flange on a tubular article.
In more general terms, the present invention relates to a mold and a method of producing a tubular plastic article with a flange thereon. While the invention was intended for the production of an automotive air intake manifold with flanged pipes, it will be appreciated that the mold and method can be used to produce other flanged, tubular plastic articles.
2. Discussion of the Prior Art
Because of the characteristics of modern plastics, more and more automotive parts are being produced using plastic. Many parts such as tubular joint covers, dashboards and intake manifolds are produced by blow molding. An intake manifold is a relatively complicated part, including a tubular body, outlet pipes and flanges on the outer free ends of the pipes for mounting the manifold on an engine block. It is difficult to blow mold such a manifold in a single molding operation. The pipes are at an angle to the body of the manifold, and controlling the tolerances of the flanges in a blow molding step is difficult. In the past, the problem was solved by the use of a so-called "lost-core process", which involved the use of a low melting point metal insert in an injection molding method, the core being melted after molding to yield a hollow manifold. More recently, the metal has been replaced with a soluble plastic which is removed from the molded part by dissolving it with hot water. In either case, the process is complicated and expensive.